/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.response.transform;

import java.io.IOException;

import org.apache.solr.common.SolrDocument;
import org.apache.solr.request.SolrQueryRequest;

/**
 * A DocTransformer can add, remove or alter a Document before it is written out
 * to the Response. For instance, there are implementations that can put
 * explanations inline with a document, add constant values and mark items as
 * being artificially boosted (see
 * {@link org.apache.solr.handler.component.QueryElevationComponent})
 * 
 * <p/>
 * New instance for each request
 * 
 * @see TransformerFactory
 * 
 */
public abstract class DocTransformer {
	/**
	 * 
	 * @return The name of the transformer
	 */
	public abstract String getName();

	/**
	 * This is called before transform and sets
	 * 
	 * @param context
	 *            The
	 *            {@link org.apache.solr.response.transform.TransformContext}
	 *            stores information about the current state of things in Solr
	 *            that may be useful for doing transformations.
	 */
	public void setContext(TransformContext context) {
	}

	/**
	 * This is where implementations do the actual work
	 * 
	 * 
	 * @param doc
	 *            The document to alter
	 * @param docid
	 *            The Lucene internal doc id
	 * @throws IOException
	 *             If there is a low-level I/O error.
	 */
	public abstract void transform(SolrDocument doc, int docid)
			throws IOException;

	@Override
	public String toString() {
		return getName();
	}
}
